You have now learned the long-tail, the knit-on, and the cable cast-on. Let’s look at the single-edge cast-on. You can think of it as the loop-over, the one most beginners start with.
It’s not as easy to knit into as the others, and it gives a light, single edge (suitable for lace), but there will be times you’ll need it, nevertheless. It can be worked on either the right needle coming toward the left, or the left needle coming toward the right, which is one of its great advantages.
In either case, begin with a slip knot.
Now hold your yarn toward the tip of the needle. Make a loop whose tail comes back over (not under) the yarn. (If you loop the tail back under the yarn, it won’t work.)
Place that loop on the needle and pull it snug.
Make the next loop the same way.
And so on.
Tomorrow, a true double-edge cast on with good stretchability: the English Long-Tail Cast-On. This one is different. Bring a friend.